20840 ÷ 2 = 10420 R0
Let's divide 20840 by 2.

Step 1:
2 goes into 2 1 times with a remainder of 0.
Write down 1 as next digit of of the result. 
Result so far: 1
Subtract 2 from 2 to get 0.
Bring next digit (0) of the dividend behind the 0 and repeat the process: 0 / 2

Step 2:
2 goes into 0 0 times with a remainder of 0.
Write down 0 as next digit of of the result. 
Result so far: 10
Subtract 0 from 0 to get 0.
Bring next digit (8) of the dividend behind the 0 and repeat the process: 8 / 2

Step 3:
2 goes into 8 4 times with a remainder of 0.
Write down 4 as next digit of of the result. 
Result so far: 104
Subtract 8 from 8 to get 0.
Bring next digit (4) of the dividend behind the 0 and repeat the process: 4 / 2

Step 4:
2 goes into 4 2 times with a remainder of 0.
Write down 2 as next digit of of the result. 
Result so far: 1042
Subtract 4 from 4 to get 0.
Bring next digit (0) of the dividend behind the 0 and repeat the process: 0 / 2

Step 5:
2 goes into 0 0 times with a remainder of 0.
Write down 0 as next digit of of the result. 
Result so far: 10420
Subtract 0 from 0 to get 0.

The final result is 10420 with a remainder of 0.